Power cable with grounding conductors

ABSTRACT

A power cable with uninsulated grounding conductors in the interstices between the insulated conductors has a helical winding of grounding wires. The grounding conductors are urged into contact with the helical wires by beddings of resilient filler material.

United States Patent 1191 Hansen et a1. Aug. 13, 1974 [54] POWER CABLE WHTH GROUNDING 2,258,687 10/1941 Peterson 174/115 CQNDUCTQRS 3,614,300 10/1971 Wilson 174/115 3,644,659 2/1972 Campbell 174/116 X Inventors: Theodore Hansen; Thomas 3,707,595 12/1972 Plate 174/115 Moran, both of Marion, lnd. OTHER PUBLICATIONS [73] Asslgneel The Anaconda Company New G. Kardos, Development of Plastics Cables in Hun- York gary, Electrical Times, Vol. 161, No. 5, Feb. 3, 1972 [22 Filed: Apr. 26, 1973 1 1 PP NOJ 354,813 Primary Examiner-Arthur T. Grimley Attorney, Agent, or FirmVictor F. Volk [52] US. Cl 174/115, 174/36, 174/116 [51] lint. C1. 1101b 7/18, HOlb 9/02 ABSTRACT [58] Field of Search 174/ 1 15, 1 16, 1 13 R, 36, A power cable with uninsulated grounding conductors 174/ 102 R, 105 R, 106 R in the interstices between the insulated conductors has a helical winding of grounding wires. The grounding [56] References Cited conductors are urged into contact with the helical UNITED STATES PATENTS wires by beddings of resilient filler material.

1,904,472 4/1933 Kent 174/1 16 X 6 Claims, 2 Drawing Figures POWER CABLEWITH GROUNDING CONDUCTORS BACKGROUND OF THE INVENTION In electric cables with grounding conductors it has been known to fit the grounding conductors into the interstices of the insulated conductors when the cable is stranded. Such a construction is disclosed for a mining machine cable in Hansen and Wilson US. Pat. No. 3,699,238 wherein the spaces of the interstices over the grounding conductor are rounded out with neoprene filler. When one of these grounding conductors opens at some point, and this eventually happens in cables that are subjected to repeated severe flexing, it no longer shares the load of any grounding current, and, of course, when all the grounding conductors have opened, the cable is no longer grounded.

SUMMARY We have invented a cable, and particularly a flexible cable wherein a grounding conductor in an interstice may open at one or more points, and still function to carry grounding current. In fact, all the grounding conductors may be open at some points without ungrounding the present cable which comprises a plurality, such as but not limited to, three, of insulated power current conductors, stranded together; a plurality of strands of resilient filler material, which may comprise outwardly facing grooves, laid in interstices between the insulated conductors; and a plurality of uninsulated grounding conductors laid in the interstices over the strands. These are supported in the grooves when the strands comprise grooves. Our cable also comprises at least one uninsulated grounding wire wound helically around the insulated and the grounding conductors which latter are urged outwardly by the filler strands against the grounding wire, and an abrasion-resistant jacket surrounding the grounding wire.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a section of a cable of our invention. FIG. 2 shows a partial section of the cable of FIG. 1 comprising an alternative filler strand.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT A cable, indicated generally by the numeral 10, shown in FIG. 1, applies the improvement of our invention to the flexible mining machine cable disclosed in US. Pat. No. 3,699,238, incorporated herein by reference. The cable has 3 flexible-stranded 4/0 Awg tinned-copper conductors 11, 12, 13 with respective 80-mil walls of insulation 14, 15, 16 to comprise insulated power current conductors designated 17, 18, 19. The insulated conductors 17-19 are triplexed together with a left hand lay providing interstices 21, 22, 23 and a central opening 24 containing an insulated ground check strand 26. At the base of the interstices 21-23 we have laid resilient filler strands 27, 28, 29 which are conveniently formed by extruding rods of neoprene or rubber. Other materials such as twisted fibers can be used for the strands 27-29 so long as they have sufficient nerve or resiliency to continue to recover from compression for indefinite periods of time. Pasty materials or materials that are plastic in the sense that they are subject to permanent compressive deformation are not suitable for the strands '27-29. Over the strands 27-29 within the interstices 21-23 we have laid three 3 Awg grounding conductors 31, 32, 33 stranded from tinned copper wires. The size of the strands 27-29 is selected sufficiently large to project the surfaces of the conductors 31-33 radially outwardly of the circle inscribing the conductors 17-19. The illustrated cable It) is constructed to have a cylindrical outer surface. Where circularity of the cable section is not required it is at least necessary that the surfaces of the conductors 31-33 project beyond the tangent lines connecting the surfaces of the insulated conductors so that these surfaces will be urged against any wrappings that are applied around the assembled conductors. Where, as in the present cable 10, it is desired to produce a cylindrical cable, additional filler material, not necessarily resilient, may be added such as filler strands 34.

A grounding wire 36 is helically wrapped over the insulated conductors 17-19 and grounding conductors 31-33 making permanent electrical contact with the latter.

The act of wrapping the wire 36, or a plurality of such wires, compresses the adially projecting grounding conductors 31-33 into the esilient filler strands 27-29 hich thereafter maintain a pressure of the grounding conductors against the grounding wire. The wire 36 is one of seven 28 Awg wires wound in parallel with a right hand lay. It might, however, within the scope of our invention be comprised in a braided tape, or take the form of a flat wire of substantial width. The essential feature of the wires 36 is that they comprise a large plurality of electrically conducting members connecting the conductors 31-33 circumferentially at many points along the cable 10.

Over the wires 36 we have wrapped a fiber reinforced conventional binder tape 37 and extruded a neoprene or other abrasion resistant jacket 38. This is surrounded by an open weave nylon seine twine reinforcing web 39 and a second abrasion resistant extrusion 41.

In the embodiment of FIG. 2 a resilient filler strand 42 has been extruded in a shape providing a lengthwise groove 43 to support the grounding conductor 31. The strand 42 has a restricted section 44 that nests into the base of the interstice 21 and comprises more positive means of securing the continued proper positioning of the grounding conductor against the grounding wires 36. The number of strands 42 used in any cable will equal the number of interstices bearing grounding conductors.

In the manufacture of the cable 10 it is economical to apply the grounding wires 36 with the same length of lay and in the same operation as that for the application of the tape 37 and, indeed, the wires 36 may first have been bonded against the underside of the binder tape.

The foregoing description has been exemplary, rather than definitive, of the cable of our invention for which we desire an award of Letters Patent as defined in the appended claims.

We claim:

1. A power cable comprising:

A. a plurality of insulated power current conductors stranded together, interstices being formed between adjacent of said conductors,

B. a plurality of strands of resilient filler material laid in said interstices,

C. a plurality of uninsulated grounding conductors laid in said interstices over said strands,

D. at least one uninsulated grounding wire wound helically around said insulated conductors and said grounding conductors, said grounding conductors 5 being urged outwardly by said strands against and in electrical contact with said grounding wire, E. an abrasion-resistant polymeric jacket surrounding said grounding wire. 2. The cable of claim 1 wherein said plurality of insulated conductors is three.

grounding conductors is three.

l= l l 

1. A power cable comprising: A. a plurality of insulated power current conductors stranded together, interstices being formed between adjacent of said conductors, B. a plurality of strands of resilient filler material laid in said interstices, C. a plurality of uninsulated grounding conductors laid in said interstices over said strands, D. at least one uninsulated grounding wire wound helically around said insulated conductors and said grounding conductors, said grounding conductors being urged outwardly by said strands against and in electrical contact with said grounding wire, E. an abrasion-resistant polymeric jacket surrounding said grounding wire.
 2. The cable of claim 1 wherein said plurality of insulated conductors is three.
 3. The cable of claim 1 wherein said plurality of grounding conducTors is three.
 4. The cable of claim 1 wherein said filler strands define outwardly facing grooves, said grounding conductors being supported in said grooves.
 5. The cable of claim 4 wherein said plurality of insulated conductors is three.
 6. The cable of claim 4 wherein said plurality of grounding conductors is three. 